1. Field of the Invention
The present invention relates to a resonant liquid detecting device, which can be used in a viscometer, a density meter, or a liquid-level indicator, and in which a liquid detector, immersed in liquid to be measured, is resonated by a circular direction vibrator made of piezoelectric ceramic.
2. Description of Related Art
U.S. Pat. No. 4,811,593 discloses a vibration unit formed by connecting a vibration shaft directly to a circular direction vibrator and connecting a liquid detector directly to one end portion of the vibration shaft, vibrations of the vibrator being transmitted to the liquid detector through the vibration shaft for resonance.
It is necessary for the vibration unit to be suspended such that the vibration unit is vibration-wise isolated with respect to the casing for receiving a vibrator and a liquid container or liquid feed pipe containing liquid in which the liquid detector is immersed. In the above conventional device, a mass, provided on the end portion of the vibration unit opposite to the liquid detector, is hung on the casing through a vibration absorbing member such as rubber, thereby providing a suspension supporting structure (i.e., a structure for supporting the unit in a suspended fashion).
However, in order to stably hang the upper end (upper side of the vibrator) of the vibration unit with respect to the casing through the mass and to maintain the mass in a stationary state against vibration of the vibrator as in the conventional device, it is required to use a rather large-sized mass having a heavyweight relative to the weight of the overall vibration unit. Therefore, the conventional device has the problem that the overall construction becomes heavy in weight and large in size.
The conventional device can fulfill the requirement of suspending the overall vibration unit by vibration-wise isolating the unit. However, since the mass is substantially connected to the casing, it rigidly restrains (fixes) the vibrator which performs a twist vibration action. The resulting structure turns out to be an external disturbance factor which makes it difficult to obtain a stable and positive twist vibration.
The above problems must also be resolved when viscosity or density of liquid is to be measured by supporting the vibration unit on a liquid container or pipe in a suspending fashion and immersing the liquid detector in the liquid.